Question

Which set of coditions are correct for spontaneity of a electrochemical cell reaction?

• A. $\Delta G=0,\Delta E=0$
• B. $\Delta G\text{=+}ve,\Delta E\text{=+}ve$
• C. $\Delta G=-ve,\Delta E=0$
• D. $\Delta G=-ve,\Delta E\text{=+}ve$

Answer 1

Answer: (D)

Spontaneity of cell indicates that the oxidation-reduction reaction is a spontaneous reaction for reduction at the cathode and oxidation at anode. For this $\Delta G$ must be negative.

$\Delta G=\Delta H-T\Delta S$ ; $\Delta G=\Delta E+P\Delta V-T\Delta S$

For spontaneity $\left(\Delta G = - v e\right)$

$\because \Delta G=-ve$ , $\Delta E\text{=+}ve$